1. Field of the Invention
This invention relates generally to fastener driving tools, and particularly to driving tools that utilize an energy storing flywheel that selectively engages a ram in order to drive the ram into engagement with a fastener, such as a nail or a staple, in order to drive the fastener into a workpiece.
2. Description of the Prior Art
Several fastener driving tools that utilize an energy storing flywheel for the purpose of storing energy to drive the fastener into the workpiece are known. Examples of representative prior art devices are disclosed in U.S. Pat. Nos. 4,042,036; 4,121,745; 4,129,240; 4,189,080; 4,298,072; 4,290,493 and 4,323,127. Also, the copending Kerrigan application Ser. No. 476,321, filed Mar. 17, 1983 and assigned to the same assignee as the present invention, discloses a fastener driving tool wherein an energy storing flywheel cooperates with an idler wheel to selectively engage the ram and drive a fastener into the workpiece. The present invention is directed to an improved fastener driving tool of the general type disclosed in said copending Kerrigan application.
In the Kerrigan application, the flywheel, which is rotated at high speed, and the idler wheel which cooperates with the flywheel, are both rotatably mounted in a plastic housing which also supports the control switches, solenoid for controlling engagement of the ram with the flywheel, and the other components of the fastener driving tool. As a result, the impact forces generated during driving of the ram are transmitted directly to these other components of the fastener driving tool which may result in excessive wear on certain components and require substantial repair to maintain the tool in service. Additionally, it has been found that if the idler wheel is too close to the flywheel excessive wear on the ram will result which will substantially shorten the life of the ram and require its replacement. On the other hand, if the idler wheel is too far from the flywheel insufficient force will be imparted to the ram to enable it to drive a particular fastener to the required depth in the workpiece. Accordingly, it would be desirable to provide a readily accessible adjustment of the separation between the idler wheel and the flywheel so that optimum driving conditions can be achieved and maintained. However, such optimum conditions, once achieved, should be maintained despite the impact forces developed while driving a fastener, until the next separation adjustment is required to accommodate a different workpiece or the like. The Kerrigan application provides an eccentric member to adjust the separation between the idler wheel and the flywheel. Such adjustment is, however, not readily accessible and requires special tools to effect the adjustment.
It has also been found that in a device of the type shown in the Kerrigan application the drive belt, which interconnects the flywheel with an electric motor and drives the wheel at high speed, absorbs substantial shock when the high speed flywheel engages the ram and requires an optimum tension to maintain optimum driving conditions for the flywheel. If, for example, the drive belt is replaced, it may be installed with too great a tension which will result in excessive wear and short life of the drive belt. On the other hand, the drive belt absorbs substantial shock when the flywheel engages the ram and may tend to loosen with usage. If the tension in the drive belt becomes too small, then optimum driving conditions for the flywheel are not provided. Accordingly, it would be desirable to provide means for automatically establishing the optimum value of tension in the drive belt.